(1) Field of the Invention
The present invention relates to a method for fixation of optical fiber in an optical device module and a fixation pipe. In particular, it relates to a method and a fixation pipe for fixation of optical fiber in an optical device module, which has the narrowed interior space between an optical modulator, which is an optical element, and the case incorporating it, such as an optical modulator module.
(2) Related Art Statement
Corresponding to the increasing demand for recent high-speed and high-capacity information communication, dense wavelength division multiplexing (DWDM) of optical networking has been adopted more and more. Accordingly it is necessary to utilize a multitude of optical elements, such as an optical modulator, by combining them. Particularly it is required to prevent expansion of the whole equipment by miniaturizing each part of the optical device module that incorporates these optical elements, and make the whole equipment compact.
To miniaturize the optical device module, the miniaturization of the case that determines the outer shape of optical device module is needed, and to say nothing of miniaturizing the optical element itself, the distance between the optical element and the side plate of the case has to be shortened.
On the other hand, as to the optical device module, it is necessary to combine optically the optical element incorporated into the case with the optical fiber installed from the outside of the case, and therefore, in the part where the optical fiber penetrates the side plate of the case, the optical fiber is fixed, and for the purpose of sealing the inside of the case, the optical fiber is fixed by means of a solder.
FIG. 1 shows the conventional example of the method for fixation of optical fiber in the optical device module, concerning said nodule incorporating an optical modulator that is an optical element. For the sake of comprehensible coupling structure, FIG. 1 shows only the condition of the optical element 1 and the optical fiber 5 that are adjacent to the side plate 11 of the case 10.
The optical modulator 1 consists of the chip 2, on which an optical circuit, such as an optical waveguide, is formed, and the stiffening plate 3 for assisting in the binding of said chip 2 and the capillary 4. The capillary 4 is the member that makes the optical fiber 5 penetrated and retained, and the capillary 4 and the optical modulator 1, and the capillary 4 and the optical fiber 5, respectively, are joined together after optical positioning.
The optical modulator 1 is fixed to the inside of the case 10 that is to compose a module, and the optical fiber 5 penetrates the side plate 11 of the case 10 and is derived to the outside of the case. Normally the side plate of the case 11 is equipped with the fixation pipe 8 for fixing optical fiber, and the optical fiber 5 is configured to penetrate into said fixation pipe 8 further. Also, to position the optical fiber in the fixation pipe, with the coated part of the optical fiber 6 sandwiched by the sleeve (divided sleeve) 9 that is divided into two (it is divided into above and below in FIG. 1), said divided sleeve is inserted to the fixation pipe 8.
Furthermore, the optical fiber 5 is fixed at the tip of the fixation pipe 8 by means of the solder 7 and keeps the inside of the case 10 in sealing condition. In order to assist in the fixation like this of the optical fiber by the solder 7, a metallization processing is performed on the surface of the optical fiber 5, and accordingly, the adhesiveness with solder gets improved.
Likewise, as to the fixation of the optical fiber by the solder in a case, due to the sticking fixation pipe 8 inside the case, it is impossible to locate the optical modulator 1 that is an optical element, and the side plate of the case 11 closer to each other than the fixed distance and it makes it difficult to miniaturize the optical device module.
Moreover, as the fixation pipe and the optical fiber are fixed by using a solder, it is essential to position a copper bit and the solder to the appropriate place of the fixation pipe when fixing the optical fiber.
In addition, the coated part 6 consisting of the materials, such as polyethylene and nylon, is installed in the optical fiber 5 to protect the optical fiber, and in case of fixing the optical fiber by a solder outside of the case, there has been a problem that the heat of said solder is transferred to said coated part and it makes the coating materials transformed, and accordingly, the function as coated part gets deteriorated.